<p>If you try to read a value from a dictionary using a key that doesn’t exist, Swift will send you back <code>nil</code> – nothing at all. While this might be what you want, there’s an alternative: we can provide the dictionary with a default value to use if we request a missing key.</p>
<p>To demonstrate this, let’s create a dictionary of favorite ice creams for two people:</p>
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<p><span class="keyword">let</span> favoriteIceCream <span class="operator">=</span> <span class="punctuation">[</span></p>
<p>  <span class="string">"Paul"</span><span class="punctuation">:</span> <span class="string">"Chocolate"</span><span class="punctuation">,</span></p>
<p>  <span class="string">"Sophie"</span><span class="punctuation">:</span> <span class="string">"Vanilla"</span></p>
<p><span class="punctuation">]</span></p>
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<p>We can read Paul’s favorite ice cream like this:</p>
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<p>favoriteIceCream<span class="punctuation">[</span><span class="string">"Paul"</span><span class="punctuation">]</span></p>
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<p>But if we tried reading the favorite ice cream for Charlotte, we’d get back nil, meaning that Swift doesn’t have a value for that key:</p>
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<p>favoriteIceCream<span class="punctuation">[</span><span class="string">"Charlotte"</span><span class="punctuation">]</span></p>
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<p>We can fix this by giving the dictionary a default value of “Unknown”, so that when no ice cream is found for Charlotte we get back “Unknown” rather than nil:</p>
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<p>favoriteIceCream<span class="punctuation">[</span><span class="string">"Charlotte"</span><span class="punctuation">,</span> default<span class="punctuation">:</span> <span class="string">"Unknown"</span><span class="punctuation">]</span></p>
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